Printing-plate-casting machine.



R. T. JOHNSTON.

1 PRINTING PLATE CASTING MACHINE.

APPLICATION FILED NOV. 17, 1913.

Patented Feb. 2, 1915.

THE NORRIS PETERS CU., FIIUIIO'LITHOH WASHINGTON. D. C.

UNITED STATES PATENT OFFIQE.

ROBERT T. JOHNSTON, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE GOSS PRINTING PRESS COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

PRINTING-PLATE-CASTING- MACHINE.

Specification of Letters Patent.

Patented Feb. 2, 1915.

Application filed November 17, 1913. Serial No. 801,468.

To all whom it may concern: t

Be it known that I, ROBERT T. J oHNsToN, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and use+ ful Improvements in Printing-Plate-Casting Machines, of which the following is a specification, reference being had to the accompanying drawings.

This invention relates to improvements in printing plate casting machines.

Many processes differing more or less from each other have been employed for producing printing plates. By some proc esses the plate is cast entire in an appropriate mold, either cast curved for use in that condition or cast flat for use on a flatbed press or to be curved by a subsequent operation for use on a cylinder press. By other processes, a metal printing face is produced in the form of a shell, which shell it is necessary by a subsequent operation to back up properly to strengthen it for use. A much-used method of backing up such a shell comprises the placing of the shell in position in a casting-box so that the shell itself forms the front face of the plate, the rear face of which is defined by the back of the casting-box or mold.

In most cases it is highly important to cool the finished printing plate as rapidly as is consistent with good workmanship. However, it has always been found necessary to cool the printing face of a cast plate gradually up to a certain well-recognized limit in order to prevent a distortion of the figures upon the plate such as to render the plate imperfect or even useless. It has therefore been the practice to protect the face of the plate against rapid cooling, while at the same time the back of the plate has been cooled much more rapidly. To this end, the back of the casting box or mold has been formed of metal, usually iron, and steps have been taken to bring about a rapid cooling of the back of the casting box, very often by the expedient of forcing water into contact with the back of the casting boX. The result of this has been that the back of the plate so chilled has had a mottled appearance and has shrunk irregularly so as to produce a varied thickness through the plate. To counteract this irregularity in thickness, in order that the plate might be of the required. thickness so as to lbring the printing face of the plate prelcisely at the desired point when the plate as applied to a press, it has been customary to provide the back of the plate in casting =with a plurality of ribs by reason of which ;the effective thickness of the plate has been made slightly greater than the desired thick ness. Then by a subsequent operation the ribs have been planed 0r shaved off to bring the effective thickness of the plate to precisely the dimensions desired.

It is one of the objects of my invention to provide means by the use of which a plate may be cast of the desired effective thickness without the necessity for the shaving operation.

It is another object of my invention to improve devices of this type and the plates produced thereby so as to enable the plates to be more readily cooled by conduction from the rear faces of such plates.

It is still a further object of my inven tion to improve devices of this type in sundry details hereinafter pointed out.

I have been enabled to avoid the necessity for the shaving operation by the expedient of protecting the faces of the ribs of the newly cast plate while it is still in the casting-box so that such ribs are not permitted to cool so rapidly as to render them uneven and unreliable. I have accomplished this result in the manner described in my allowed application, Serial No. 7 26,976, of which application this application is in part a continuation. In the apparatus there shown, the grooves in the back of the casting-box or mold are considerably deeper than is necessary for the formation of the bearing ribs on the back of the plate, each of such grooves being provided with a member composed of material which is a very poor conductor of heat, the poor heat conducting member, of course, being proportioned so as to secure the desired aggregate thickness of plate and rib. I have accomplished this same result also in the manner illustrated herein, in which the faces of the bearing ribs of the plate are cast against metal rings which are insulated from the rear face of the back of the casting box, thus preventing almost entirely any cooling of such rings by conduction through the back of the casting-box, while at the same time preserving the advantage of having the bearing ribs of the plate cast against a metal surface rather than against a softer surface of papier-mach or similar poor heat conducting substance.

In the drawings,Figure l is a cross-sectional view of the back of a casting-boX and a printing plate in position thereagainst, partly broken away, illustrating one form of my improved apparatus, the casting-box being preferably of the type adapted for producing curved plates; and Fig. 2 is a similar view of such a casting-box and printing plate showing a modified construction.

In Fig. 1, 10 indicates ametal plate forming the back of casting-box, provided with heat-radiating ribs 11 on its outer face. 12 indicates a plurality of grooves in the inner face of said plate 10, said grooves being almost completely filled by the blocks of poor heat-conducting material 13 which form the operative bottom faces of said grooves. 14 indicates a printing plate, the upper printing face of which is produced in any suitable manner. ribs formed on the back of the printing plate 14 against the faces of the poor heatconducting members 13.

As will be readily understood, when the molten printing plate metal is poured into the casting-box, that portion of the molten metal which comes in contact with the metal plate 10 will be readily cooled by reason of the fact that such plate 10 is a very good conductor of heat. But the faces of the ribs 15 cannot be so readily cooled by reason of the fact that the members 13 are poor conductors of heat. It therefore follows that, while the printing plate 11 as a whole can be cooled almost as rapidly as though the members 13 were not employed, the cooling of the faces of the ribs 15 is very materially retarded and rapid cooling of such faces is prevented. The result is that the ribs 15 do not become cold-shot or chilled, or mottled in appearance, in the manner above described which is objectionable for the reasons above stated, but the cooling is caused to proceed more slowly at such a rate that the metal shrinks evenly. Inasmuch as the members 13 are all located and proportioned so that their faces are at the same distance from the printing face of the plate produced, it follows that the aggregate thickness of the printing plate 1e and the ribs 15 is uniform throughout the plate 14-. The proportions being such also as to produce a plate 14.- the effective thickness of Which, that is to say, the aggregate thickness of the plate proper and of the ribs,conforms to the thickness of plate desired for use on a press, there is no need for shaving the ribs of the printing plate after it is removed from the casting-box.

In Fig. 2, which shows a modified form of my invention, 16 indicates the metal plate forming the back of the casting-box and 15 indicates the r rings themselves.

vided with a plurality of grooves 21 spaced a short distance apart running parallel with the grooves in which the insulated rings 19 are located. 22 indicates the plate cast in the casting-box against the back 16, comprising the bearing ribs 23 cast against the rings 19, and provided also with smaller ribs parallel thereto caused by the use of the grooves 21 in the back 16. 7

By the use of the insulated metal rings 19, those portions of the operative face of the back against which the bearing parts of the plate are cast are protected against direct cooling by conduction through the back just-as are the portions 12 of the operative face of the back 10 shown in Fig. 1. But at the same time in the use of the construction shown in Fig. 2, the metal rings 19 positively retard the cooling of the bearing rings 23 by reason of the heat stored in the In the use of the insulated rings '19, therefore, not only must the 1 faces of the ribs 23 becooled by conduction through the printing plate itself rather than by conduction directly through the back 16, but both the bodies of the rings 19 and the faces of the ribs 23 must be cooled in this manner byconduction through the printing plate rather than by conduction directly through the back 16.

By the provision of the smaller ribs be- 7 tween the bearing ribs 23, the plate 22 is given a greatercontact surface with the back 16 and consequently the cooling of the main portion of the plate by conduction through the back 16 is enhanced. Moreover, after the cast plate 22 has been removed from the casting-box, the presence of the small ribs between the bearing ribs 23 gives a greater cooling surface for contact of the water which is played directly upon the plate, causing a saving in the time necessary for the complete cooling of the plate.

By reason of this invention, doing away with the necessity for shaving the ribs of the plates produced, a very material saving of time in the preparation of a plate is effected, which, as said above, is of very great importance, especially in the preparation of the plates for the run of a daily newspaper.

lNhile I have not shown means for protecting against rapid cooling any part of the cast plate except the bearing parts in the form of ribs, it will be understood that I do not restrict my invention to this particular form of structure, eXcept as hereinafter specifically claimed, the essential feature of my invention being in part the use of means for protecting against too rapid cooling the portion or portions of the cast plate by which the plate is supported upon a press, and my claims are to be construed accordingly.

hat I claim as my invention, and desire to secure by Letters Patent, is

1. A back for a casting-box for printing plates, comprising a. portion the operative face of which is adapted to be cooled readily by conduction through the back and another portion against which the bearing part of the printing plate is cast the operative face of which is not adapted to be cooled readily by conduction through the back.

2. A back for a casting-box for printing plates comprising a portion the operative face of which is formed of a good heat conductor, and comprising a portion against which the bearing part of the printing plate is cast the operative face of which is adapted to protect such bearing part against rapid cooling.

8. A back for a casting-box for printing plates, comprising a portion the operative face of which is formed of a good heat conductor, and comprising a portion against which the bearing part of the printing plate is cast the operative face of which is adapted to cool slowly relative to the rate of cooling of the remainder of the back.

4. A back for a casting-box for printing plates comprising a portion against which the greater part of the printing plate is cast adapted for quickly cooling that part of the printing plate by conduction through the back and comprising another portion against which the bearing part of the printing plate is cast not adapted for quick cooling by conduction through the back.

5. A back for a casting-box for printing plates formed with a portion the operative face of which is adapted to be cooled readily by conduction through the back and another portion against which the bearing part of the printing plate is cast comprising poor heat conducting material whereby such lastnamed portion is not adapted to be cooled readily by conduction through the back.

6. A back for a casting-box for printing plates, formed of a portion the operative face of which is adapted to be cooled readily by conduction for cooling the cast plate, and other portions the operative faces of which are adapted to cool relatively much more slowly after a casting operation for retarding the cooling of the corresponding portions of the printing plate in contact therewith.

7 A back for a casting-box for printing plates, comprising a portion the operative face of which is adapted for cooling readily by conduction through the back for cooling the cast plate, said back being provided with a plurality of grooves on its operative face, the operative bottom faces of which grooves are adapted to cool relatively much more slowly whereby the cooling of the faces of the correspondingly-shaped ribs formed on the cast plate is likewise slowed down.

8. A back for a casting-box for printing plates comprising a portion the operative face of which is formed of good heat conducting material, and another portion the operative face of which is insulated from the rear face of the back.

9. A back for a casting-box for printing plates comprising a portion the operative face of which is formed of good heat conducting material, and another portion the operative face of which comprises good heat conducting material and means for insulating said last-named good heat conducting material from the rear face of the back.

10. A back for a casting-box for printing plates having a recess in its operative face, and comprising a member mounted in said recess and partially filling the same, said member being protected against being cooled readily by conduction through the back.

11. A back for a casting-box for printing plates having a recess in its operative face, and comprising a member mounted in said recess and partially filling the same against which the bearing part of the printing plate is adapted to be cast, said member being adapted to protect the face of the bearing part of the cast plate against rapid cooling by conduction through the back.

12. A back for a casting-box for printing plates having a recess in its operative face, and comprising a member mounted in said recess and partially filling the same adapted to lose its heat much more slowly than the remainder of the back as said back is cooled by conduction from its rear face.

13. A back for a casting-box for printing plates having a recess in its operative face, and comprising a member mounted in said recess and means for insulating said memher from the remainder of the back whereby said member is adapted to lose its heat much more slowly than the remainder of the back as said back is cooled by conduction from its rear face.

14. A back for a casting-box for printing plates having a recess in its operative face, and comprising a member of good heat conducting material mounted in said recess and insulated from the remainder of the back adapted to lose its heat much more slowly than the remainder of the back as said back is cooled by conduction from its rear face.

15. A back for a casting-box for printing plates formed of metal and having a recess the Walls of said recess.

16. A back for a casting-box for printing plates having a plurality of grooves in its, operative face, and comprising a plurality oi members of good heat conducting mate rial mounted in said grooves and partially 10 filling the same and means for insulating said members from the mam portlon of the back and from the rear face thereof.

ROBERT T; JOHNSTON.

Witnesses:

W. H. DE BUSK, W. A. FURNNER.

Copiesofthis patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, I). G. 

